The Convair Observational Satellite was developed during the Empire Mars-Venus mission study. The Convair Observational Satellite was based on designs by Krafft Ehricke who was a pioneer of the modular spacecraft concept that showed that from a relatively small number of standard modules a large and varied number of spacecraft could be custom assembled for whatever special purpose was required. The Convair Observational Satellite was to not only to be used for exploration of the solar system but was also designed to orbit the earth at 600 miles altitude. It was to be manned by four astronauts and was approximately 400 feet in length. The Empire project was the first large scale study of manned Mars and Venus missions. Ehricke was a prolific and innovative designer of spacecraft and space stations, He died in 1984.